Regarding your example of waiting for N records to come back, it is definitely worth it to pack all those requests into a single AJAX/JSON request. Not only are you saving the overhead of the HTTP requests (browsers can only make a 2-4 requests concurrently) but your code will be cleaner. (e.g. no counter in on the callback)
To the OP: can you post more details about what you're trying to do when you end up with so many callbacks? It sounds like things could be make cleaner using objects and callback methods instead of having tons of nesting code blocks. On Mar 7, 6:41 pm, timothytoe <[EMAIL PROTECTED]> wrote: > I had a case where I had to wait for n records to come from the > server. They all had the same callback, which incremented a > counter.and checked to see if this load was the last one. It worked, > but I have thought about giving the whole lists of requests to the > server at once and having the server put together one large response > instead of n small ones. > > I've had other cases that were more complex where I used a bitfield > instead of a bunch of logic to see if the required pieces had come in > yet. > > I've not come up with anything I like in jQuery animation-wise. When > it's just one thing I'm animating in jQuery, I'm happy. When it's > more, I end up with a big mess. I'm not sure what I'm looking for, but > I'm really starting to hate jQuery's nested animation system because > it's such a pain to change things around once you've done the work. > > On Mar 7, 2:19 pm, Shawn <[EMAIL PROTECTED]> wrote: > > > This plugin was suggested in another thread: > > >http://plugins.jquery.com/project/ajaxqueue > > > While it's close, my initial read of it suggests it doesn't do quite > > what we're looking for here. I'll have to play with it to be sure though... > > > Shawn > > > Hamish Campbell wrote: > > > Sounds like some sort of ajax queuing plugin is in order. Would have > > > to be more complex than animation queues. > > > > eg, queue constists of a 1-d array. Each element in the array can be a > > > request, or an array of requests (that execute simultaneously). The > > > queue pops the first element, performs the call (or calls), checks for > > > completion then pops the next one. Errors return the queue position, > > > or perhaps there is an array of error callbacks? > > > > On Mar 7, 1:30 pm, Shawn <[EMAIL PROTECTED]> wrote: > > >> I have a similar situation and am watching this thread in hopes > > >> something useful may come of it. > > > >> What I've done for now is the nested calls. I use a common > > >> errorHandler() function that takes in the element to show the message > > >> with and the message itself. The message tends to be the .responseText > > >> of the XHR object more often than not. But this still feels clumsy. > > > >> What I've considered doing is to create a temporary structure that would > > >> contain flags for each of the sub processes. The success function for > > >> each sub process would set its flag as being "complete" and then call > > >> the final update function. This final update function would check each > > >> of the flags and when all are set do whatever final processing (if any) > > >> is needed. > > > >> For instance, I need to a) get a list of employees, b) get a list of > > >> tasks for all employees, c) render a table for the employees tasks and > > >> apply some code to give the table a fixed header and column. I already > > >> have existing routines to get the employees and tasks, so can reuse > > >> these here. So my code may potentially look like this: > > > >> var mydata= { > > >> flags: { employees: false, tasks: false }, > > >> employees = [], > > >> tasks = [], > > >> render: function () { > > >> //don't continue if we don't have enough data > > >> if ( !mydata.flags.employees || !mydata.flags.tasks ) { return; } > > > >> //code to render the output goes here. > > >> ... > > >> } > > > >> }; > > > >> $.ajax({ > > >> url: "getEmployees.php", > > >> dataType: "json", > > >> success: function (json) { > > >> mydata.employees = json; > > >> mydata.flags.employees = true; > > >> mydata.render(); > > >> } > > > >> }); > > > >> $.ajax({ > > >> url: "getTasks.php", > > >> dataType: "json", > > >> success: function (json) { > > >> mydata.tasks = json; > > >> mydata.flags.tasks = true; > > >> mydata.render(); > > >> } > > > >> }) > > > >> obviously this is not throughly thought out yet, and has room for > > >> optimizations (I don't think the flags are really required if you just > > >> check the data properties instead). But what this would allow is the > > >> two ajax requests to be run concurrently and still have the same output. > > >> Which ever Ajax request finishes last fires the rendering (and it > > >> doesn't matter which). > > > >> The nested approach would take twice as long (by may be more reliable?) > > >> as the second request isn't made until AFTER the first has been > > >> completed. This may be a moot point for this sample problem, but I know > > >> I have a couple places where 4 or 5 Ajax requests are needed to complete > > >> one task. > > > >> The problem here is that event handling is not taken care of > > >> automagically. Each Ajax request would need to handle this itself. But > > >> this entire process could in theory be wrapped up into a single > > >> function. I guess the real question is if that function can be > > >> abstracted enough to make it generic. Right now, I don't see how. > > > >> I don't think this idea is revolutionary or anything. Probably kinda > > >> obvious and/or flawed. But perhaps it'll get you (us?) moving in a > > >> positive direction. > > > >> Now I'm curious though and want to try out some things... I'll report > > >> back if I have any success... > > > >> Shawn > > > >> h0tzen wrote: > > > >>> On 5 Mrz., 15:40, J Moore <[EMAIL PROTECTED]> wrote: > > >>>> wouldn't nesting the methods work? e.g. > > >>> unfortunately not as some methods have to be invoked in parallel. > > >>> generally exactly this nesting looks fine with no real code behind > > >>> but it is just cruel if you imagine having error-handling, rollbacks > > >>> and business logic etc within. > > >>> what im looking for is some pattern abstracting the async-callbacks > > >>> or just a real-world example/solution of someone having the same > > >>> issues with logic involving multiple, dependent ajax-calls. > > >>> thanks, > > >>> kai- Hide quoted text - > > >> - Show quoted text -
